Influence of water temperature on oxygen consumption and ammonia excretionof juvenile pikeperch, Stizostedion lucioperca (L.) reared in a recirculating system

The oxygen consumption and ammonia excretion rates of fed and starved finge rling pikeperch, Stizostedion lucioperca (L.), reared in a recirculating sy stem were measured at water temperatures of 20 and 24 degrees C. The fish w ere fed a commercial trout diet for 18 h day(-1) (0900-0300 h) at daily rat ions of 3.0% and 3.5% body weight at 20 and 24 degrees C, respectively. The mean rates of oxygen consumption (OC) (mg O-2 kg(-1) h(-1)) of fed fish we re 225.3 at 20 degrees C and 356.2 at 24 degrees C, and were significantly different (P < 0.001). The mean OC rates (mg O-2 kg(-1) h(-1)) of starved f ish were 106.3 at 20 degrees C and 145.9 at 24 degrees C, and these values also differed significantly (P < 0.001). The average ammonia excretion (AE) rates of fed fish were 14.1 and 18.3 mg TAN kg(-1) h(-1) at 20 and 24 degr ees C, while the rates for the starved fish were nearly 10-fold lower, i.e. 1.4 and 2.0 mg TAN kg(-1) h-(1). These rates differed significantly with t emperature for both the starved and fed groups of fish (P < 0.01). The mean oxygen:feed ratio (OFR) for fish cultured at 20 degrees C was 0.172 kg O-2 kg(-1) feed fed day(-1), while at 24 degrees C, it was 0.234 kg O-2 kg(-1) feed fed day(-1). The ammonia:feed ratios (AFRs) were similar for the fish held at the two temperatures, i.e. 0.011 and 0.012 kg TAN kg(-1) feed fed day(-1).